The growing demand for real-time streaming video on portable devices has increased the importance of multimedia multicast in wireless networks, such as mobile wireless networks. Multiple-input and multiple-output (MIMO) is a technology that utilizes multiple antennas at a transmitter and/or receivers to improve communication performance.
Space-time block coding (STBC) is a technique often used in conjunction with MIMO in wireless communications to transmit multiple copies of a data stream across a number of antennas and to exploit the various received versions of the data to improve the reliability of data-transfer and/or the amount of data transferred in a given bandwidth. STBC code is generally constructed according to agreed upon transmit and receive antenna configurations.
Hence, STBC cannot adapt to client antenna heterogeneity, as the number of transmit and receive antennas must be known for successful reception by all target receiving devices. Thus, as devices with different numbers of antennas are likely to coexist, the spatial multiplexing gain of the entire multicast group is limited by the device with the fewest number of antennas. The cost of tracking the hardware capabilities of receivers can be excessive in the presence of a high client churn. Hence, conventional multicast transmitters must be conservative in employing additional spatial dimensions so that all devices in the multicast group can properly receive a multicast transmission.
Additionally, different mobile devices, including smart phones, tablets, and laptops, have diverse screen sizes that result in resolution heterogeneity. Thus, screen size and other device capabilities may further limit the types of multicast transmissions that can be properly displayed by each device in the multicast group.